sudden nitrite spike

[ram_g0p]

25 Gal planted tank 3 months old. Fish rasboras (7) tetras (cardinal 3; neon 2). The GH numbers are ~150 PPM. The KH values: 40-80 ppm. pH6.5-7.0
ammonia 0 ppm

Now, I was alarmed my nitrite was ~3 ppm I mean I have had nitrite and ammonia at 0 ppm for a long time. Admittedly, I have not done water params test in 2-3 weeks. My nitrate is at 20 ppm and I do dose nitrate as per PPS method, only alternate days. So why this (sudden) increase in nitrites??

BTW, about 2 days ago I took some of this tank water, during water change, and put it in my 2.5 gal tank as I going to quarantine my new fish (cardinal tetras 5). The nitrite level in that water is close to 0 ppm!

Only other thing I did to my main tank at water change:
I put about 10 gelatin capsules full of Osmocote Plus. Also, I did some very minor replanting: shifted a small amazonsworda few inches to give more light. And I planted most ofanacharis, which were floating since purchase (~3 wks) at a corner.
Other than that, yesterday I dosed Fluorish Comprehensive (lower dose ~1 mL) and Fluorish iron (again ~1 mL), in addition to my usual PPS dosing (potassium, nitrate,phosphate). That too, I dose them lower than recommeded for my tank.

I did 20% water change this morning. Not much change in nitrite level, understandably. Will do another 20% tomorrow morning. In all this, my fish are doing OK, apparently. Even my cardinal tetras.

Is there something in that would lead to give false nitrite level? I plan to do some tests separately, combing various ferts solutions I used - PPS solution, Flourish Comp, Fluorish etc - at different combinations and see if there's any effect. I ran out of test strips, so will have to wait.

Thanks all...

 

[librarygirl]

Did you move the substrate at all when you shifted things around? Plant matter and waste can get under the substrate (particularly if it's gravel) and decay and then once it's disturbed it can release all kinds of things into the water. Do you vacuum the substrate regularly?

I'd get a liquid test kit (API Master) instead of the strips which aren't very accurate.

In the meantime, do a couple of 50% water changes to get that level down. Hopefully things will settle in a few day but keep doing water changes until you can get a test kit to be sure. I doubt the ferts would add nitrite to the tank.

 

[ram_g0p]

I didn't move the substrate much. Just a minimal disturbance, I would say. I will do some 20% water change tomorrow as well. Should I go ahead and vac the substrate as well? My substrate is gravel + FloraMax and some Eco-Complete. Being a planted tank I don't want mess with the substrate too much. Actually, I got some dwarf hairgrass today, but didn't plant due to the current situation. I have placed them in a glass jar water and gravel. Some planted and most floating. Hopefully, they will OK for next few days. I have got API Master Kit ordered. Thanks for your time and help.